Diazotization in presence of developer



DIAZGTIZATION IN PRESENCE OF DEVELOPER Louis I. Fideil, Bound Brook, N.J., assignor to American Cyananiid Company, New York, N.Y., a corporation of Maine No Drawing. Filed Nov. 15, 1955, Ser. No. 547,035

5 Claims. (Cl. 8-48) The present invention relates to a new method of preparing azo dyestuffs directly on the fiber to be dyed. The azo dyestuffs have been known for over 60 years.

rates atent Q It is common practice to form the color in situ on the fiber by dyeing or by impregnation with an amine followed by diazotizing and then development with another amine or phenolic body. The diazotization of an amine is a. process known to take place best in the presence of a mineral acid,

aqueous medium The coupling reaction of the diazonium salt is very 1 slow or substantially absent in mineral acid solutions, but is rapid in neutral or weakly alkaline solutions. The diazonium salt in neutral or alkaline solutions is usually unstable and decomposes readily to a phenol,

nitrogen and other products. This decomposition is rehas two effects: (1) the coupling rate increases, and

(2) the rate of diazo decomposition increases even faster. Thus, dining the coupling reaction, as during formation of the diazonium salts, it has been customary to keep the reaction mixture cold.

I have now discovered that diazotization can be accomplished in the absence of mineral acid and coupling effected simultaneously if a developer is present in solution. This new reaction involves replacing the mineral acid with acetic acid and raising the temperature. Diazotization, followed by immediate coupling, will then take place at elevated temperatures. The convenience of dyeing fabrics by this process is obvious. Only a single combined diazo and developing bath is required and the necessity to refrigerate the diazo bath is eliminated.

In the prior art procedure of diazotizing and developing cotton dyed with direct diazo colors, it is customary to dye the material, rinse, diazotize with mineral acid and sodium nitrite, rinse and then develop with any suitable developer in an alkaline bath. The alkalinity of the developing bath is usually obtained by dissolving the developer in an alkali, such as caustic or soda ash.

In the case of cellulose acetate, the dyeing and diazotizing procedures are followed as for cotton; however, the developing is usually carried out in a bath which is acid rather than alkaline. 'The developer used on acetate is usually beta hydroxy naphthoic acid. This is dissolved with a sufficient amount of alkali, caustic soda, sodium acetate, soda ash, or ammonia. The alkaline solution is neutralized with acetic acid or the beta hydroxy naphthoic acid is dispersed without dissolving in alkali. The

500013168 immediately.

2 acidity ofxthe beta hydroxy naphthoic acid itself is suificient to make the condition of the bath satisfactory for coupling with the diazo of the dye. Y

My new process is faster than the prior art method because the separate steps of diazotization and rinsing out the nitrous acid are not required.

Undersirable side reactions, such as formationof diazoamino compounds in the diazotization step and decomposition of the diazo compound to phenol, followed by coupling to form unwanted dye, are reduced to the minimum by the present process.

I have made dyeings of navy blueand black by my new procedure and find that, if the temperature is not sufficiently high, insuflicient diazotization and coupling take place; However,'-there is no destruction of diazo, as increasing the temperature of the same process and continuing the diazotiz ing period or developing period produces satisfactory results. I In one method of practicing my invention, nitrite of 'sodais added 'to an acetic acid-solution of the developer and the temperature is adjusted until nitrous acid is formed. Any watersoluble nitrite other than sodium nitrite can equally well be used but this is preferred because of its availability. The base is added either as a dispersion, or a solution. As the base is diazotized, it

The rate of diazotization is controlled by the temperature, which is raised until the-reaction is completed. When dyeing acetate, the tempera- .ture of 180 'F. in the presence of acetic acid-will produce complete diazotization and beta hydroxy naphthoic acid developing. A dispersing agent may be present.

' The temperature of the development must 'be above Higher temperatures will give complete formation of the dye at a faster rate and in many cases, as .indicatedabove, a temperature of 180 F. is most effective.

The fibers which can be dyed by my process -include acetate rayon and the superpolyamides (known as nylon) such as hexamethylene diamine polyadiparnide.

My inventiontwill be further illustrated by the following examples in which the parts are 'by weight.

Example 1 One part of cellulose acetate is dyed in 30 parts of a dyebath, containing 0.40% dianisidine, for one hour at 180 F. The shade is practically a colorless ecru.

Five grams of the above dyed and rinsed material is treated in an aqueous bath containing:

parts water .500 part nitrite of soda .075 part beta hydroxy naphthoic acid .025 part caustic soda .500 part glacial acetic acid The dyed cellulose acetate is entered at 68 F. and worked while the temperature is raised to F.

The colorless cloth changes from a light red, dark red and violet to a deep bright navy blue shade similar to the shade obtained when this dye is applied by conventional procedure of dyeing, rinsing, diazotizing, rinsing, and then developing in a separate bath.

The beta 'hydroXy naphthoic acid in dispersion or solution can be added at any time prior to or after the other ingredients, but preferably before raising the temperature.

Example 2 A solution of 0.4 part acetate diazo black, which has the following composition:

CQH OH z i H in 300 parts of water is dyed on parts of cellulose acetate in a dispersed aqueous dyebath at 160 F. to 180 F. for one hour. The weight ratio of fiber to dyebath is 1:30.

' The deep yellow-orange material is entered-into a bath at 68 P: which contains 0.2 part beta hydroxy naphthoic acid previously dissolved with 0.05 part caustic soda flakes, 1 part sodium nitrite and 1 part glacial acetic acid in 300 parts water.

The dyed cellulose acetate material is wo'rked'in this bath starting at 69 F. and while'raising the temperature to180F. V

The cellulose acetate changes from brown to a brownblack and finally to a deep black' shade as the temperature is raised, the final shade being 'similar to that obtained by conventional dyeing methods.

Example 3 A solution of .050 part of amido azo benzol is efiected i by boiling with .500 part of soap and partswater;

This solution is filtered through suitable cloth into a total of approximately 150 parts water r I Five parts cellulose acetate material =dyed in this bath at a maximum temperature of 180 F. for minutes. The cellulose acetate is rinsed and treated in a bath containing .075 part beta hydroxy naphthoic acid, .025 part caustic soda and .250. part sodium nitrite dissolved in 150 parts water and acidified with .100 part glacial acetic acid. Thetemperature is raised from room temperature to 180 F. while working the cellulose acetate.

The deep yellow of the dyed cellulose acetate is changed to a bright deep red of excellent uniformity and levelness.

Example 4 1 One mol of the anilide of beta hydroxy naphthoie acid I and one mol of 3-nitro-4-amino toluene are dispersed in an aqueous solution of sodium nitrite. A printing paste is made of this dispersion by the addition of a gum, such as tragacanth. This printing paste may be. printed on cellulose or synthetic fibers.

The printed cloth when dried, is in an acid atmosphere. jA brilliant red print develops as the base present on the cloth is diazotized and couples with beta hydroxy naphthoic acid.

Example 5 v To 300 parts of water is added 0.135 part of dianisidine. A 10 part by weight sample of nylon tricot is added and the bath is held at 165 F. for 30 minutes with agitation. The cloth is then rinsed and added to a bath, previously prepared, containing 0.2 part of beta-oxynaphthoic. acid and 0.05 part of sodium hydroxide dissolved in a mixture subjected to steaming of 300 parts of water, 1 part of glacial acetic acid and 1 part of sodium nitrite, at F. The temperature of the bath is gradually raised to 180 F. over 30 minutes, while working the nylon tricot. The peach color of the fabric changes to a navy blue shade. The nylon is then rinsed and dried.

This application is a continuation-in-part of my copending application, Serial No. 324,593, filed December 6, 1952, now abandoned. j

v 1. A method of dyeing synthetic fabrics selected from the group consisting of cellulose acetate and nylon which comprises immersing said fabrics in a solution of the diazo base, rinsing, and then immersing said fabrics in a second bath prepared from a water soluble nitrite, acetic acid, and 2-hydroxy-3-naphthoic acid; and heating said second bath above F. the dyeing is complete, both said baths being free of protectivecolloids.

V 2. A methodof dyeing cellulose acetate which comprises immersing said cellulose acetate in a solution of a diazo base, rinsing, and then immersing the cellulose acetate in a second bath prepared from a water soluble nitrite, acetic acid, and 2-hydroXy-3-naphthoic acid; and heating said second bath above 125 F. until the dyeing is complete, both said baths being free of protectivecol loids.

3. A method of dyeing nylon which comprises. immersing said nylon in a solution of a diazo base, rinsing, and then immersing the nylon in a second bath prepared from a water soluble nitrite, acetic. acid, and 2-hydroxy-3- naphthoic acid; and heating said second bath above 125 F. until the dyeing is complete, both said baths being free of protective colloids.

4. The process of claim 1 in which the heating of the second bath is to .a temperature of F. I

5. The process of claim .4 in which the water soluble nitrite is sodium nitrite.

References Cited in the file of this patent UNITED STATES PATENTS l 1,571,320 Clavel Feb. 2, 1926 1,646,296 Kircheisen Oct 18, 1927 2,220,129 Stott Nov. 5, 1940 2,267,770 Von Glahn Dec. 30, 1941 2,403,900 Armour July 16, 1946 2,480,775 Ryan Aug. 30, 1949 OTHER REFERENCES 7 1:

. Acetate Silk and Its Dyes, C. E. Mullin, pub. by Von Nostrand, N.Y., 1927, pp. 223-224 relied on. Textile Colorist, December 1943, pp. 551-553. Chemical Tech. of Dyeing and Printing, Diserens, vol. 

1. A METHOD OF DYEING SYNTHETIC FABRICS SELECTED FROM THE GROUP CONSISTING OF CELLULOSE ACETATE AND NYLON WHICH COMPRISES IMMERSING SAID FABRICS IN A SOLUTION OF THE DIAZO BASE, RISING, AND THEN IMMERSING SAID FABRICS IN A SECOND BATH PREPARED FROM A WATER SOLUBLE NITRITE, ACETIC ACID, AND 2-HYDROXY-3-NAPHTHOIC ACID, AND HEATING SAID SECOND BATH ABOVE 125*F. UNTIL THE DYEING IS COMPLETE, BOTH SAID BATHS BEING FREE OF PROTECTIVE COLLOIDS. 